JPS5942588B2 - Continuous casting method - Google Patents

Description

[Detailed Description of the Invention] In continuous casting, the present invention involves pouring molten steel from a subsequent charge on top of the last molten steel from a previous charge while it is still in the mold, and continuously drawing out slabs. Concerning continuous casting method.

This type of relay continuous casting method is attracting attention as a method that further takes advantage of the advantages of continuous casting, which has excellent work efficiency.
During slab drawing, breakout accidents are likely to occur due to breakage of the joint between the first charge and the second charge, and if the first charge and the second charge are made of different steel types, the joint may be damaged due to a mixture of components. It is necessary to cut off the slabs in the upper and lower ranges, which leaves problems such as poor yield.

In view of the above, the present invention aims to provide a safe relay continuous casting method that prevents breakout accidents.
In addition, this method prevents mixing of components at the joints of slabs as much as possible, so even when continuous continuous casting of different types of steel is performed,
It has the advantage of providing a high yield.

The method of the present invention is that a steel connection piece in the shape of a half pipe is inserted into the connecting part between the slabs of the first charge and the next charge with the concave side facing up, and then pulled out as a continuous slab. It is characterized by

The process will be further explained below with reference to the drawings.

■ Pausing the drawing of the slab immediately after the last gut of the previous charge has been poured from the tundish through the immersion nozzle into the cooling mold.

(2) Draw the immersion nozzle and evacuate the tanditsukar from above the mold to remove powder and slag on the hot water surface in the mold.

(2) Place a steel piece in the shape of a pipe half on the hot water surface with the concave side facing up.

As shown in Fig. 1, the size of the pipe half-shaped slab to be placed is such that it has a projected plane that is slightly smaller than the area of the mold window, and covers approximately the cross section of the slab. often,
In addition, for reasons to be described later, pipe half-shaped steel pieces do not melt away before the poured metal around them solidifies.
It is better to have some thickness.

■ Move the next charged tanker onto the mold, lower the immersion nozzle until its tip enters the recess in the pipe half-shaped steel piece, and immediately start pouring.

- After the molten metal level fills the recess of the joint piece and exceeds its upper edge, drawing of the slab is started and continuous casting is restarted.

Figure 2 schematically shows a vertical cross section of a joint where hot water from a later charge is added and cast onto a slab from a previous charge in the mold as described above, and 1 and 1 are continuous casting equipment. 2 is the molten steel of the previous charge, 2' is the solidified shell of the same, 3 is the pipe half-shaped piece of steel placed on the molten steel of the previous charge,
4 is the molten steel of the later charge.

According to the continuous casting method of the present invention, the molten steel 2 of the previous charge
Due to the cooling effect of the pipe half piece of steel placed on the hot water surface, the tip of the solidified shell curves inward and grows to embrace the pipe half piece of steel 3, as shown in the figure. Since the pouring metal from the subsequent charge fills up the area around them, these act as hook joints, and the front and rear slabs are firmly connected.

Conventional relay continuous casting does not use joints such as pipe half-shaped billets, and moreover, the method called open casting is generally used, in which molten steel from the post-charge is added without removing the powder on the surface of the pre-charge. However, according to this open casting method, during the slight delay in starting pouring of the next charge over the pouring of the previous charge, solidification near the meniscus of the previous charge occurs. However, in the method of the present invention, as described above, the inwardly curved solidified shell An intertwined connection line is formed by the concave surface of the pipe half-shaped steel piece, and
Therefore, the connection part is firmly connected without being easily damaged by pull-out force or bending moment.
Even if an accident occurs in which it takes time to drill holes after charging, there is no risk of breakage or breakout from the relay boundary, and continuous casting can be carried out safely and smoothly.

In addition, in the conventional relay casting using open casting, mixing of components at the connection between the hot metal of the previous charge and the poured metal of the subsequent charge was unavoidable.

Therefore, when continuous continuous casting is performed on steels of different compositions, about 2 meters before and after the connection boundary of the slabs must be cut off afterwards, and the advantage of continuous casting, which is excellent in yield, is diminished.

However, according to the method of the present invention, since the pipe half-shaped steel pieces are interposed as described above, it is possible to avoid mixing of the components of the respective hot water of the front and rear charges as much as possible, and it is possible to avoid cutting off the connected part after drawing. Approximately, front charge 30CrrL and rear charge 3
It takes less than 0 crn, a total of 60 crrL.

As mentioned above, the method of the present invention is most effective in preventing breakout accidents caused by breakage at the front and rear slab connections, and in improving the yield in continuous continuous casting of steel slabs with different compositions. For example, when carrying out the large method with a curved continuous casting machine for 190 mm x 1800 mm slabs, the dimensions of the solidified shell of the pre-charge in the mold that cools and shrinks during about 1 to 2 minutes during kundish exchange and the protrusion of the solidified shell on the surface of the molten metal. Considering the dimensions, the pipe half-shaped steel piece can be used as a joint piece by cutting a pipe with an outer diameter of 90 to 110 φ and a wall thickness of 3 to 8 mm vertically in half, and stopping the casting of the pre-charge. After scraping off the slag on the surface of the molten metal, place the halved pipe and start pouring the second charge with the solidified shell holding it as described above, and the molten steel of the second charge will flow into the front charge. The solidified shell and joint are poured in such a way that they are poured, and a slab connection boundary is obtained without any risk of breakout or breakage during casting and when straightening the slab with pinch rolls.

In this case, as shown in FIGS. 1 and 2, if small hook-shaped side plates 5 are attached by welding or the like at appropriate intervals along the upper edge of the pipe half-shaped steel piece 3, This has the effect of making the slab connection boundary even stronger.

Furthermore, if a notch 6 of an appropriate size is provided at the end edge of the pipe half-shaped steel piece 3 as shown in FIG. Since it is smoothly supplied and compensated through this notch, the habit of forming cavities is completely eliminated, and it is more effective in obtaining the above-mentioned strong connection.

The pipe half steel piece referred to in this specification should not be interpreted as being limited to a steel joint piece with a semicircular cross section as illustrated in the figure, but should be interpreted as a steel joint piece with a semicircular cross section as illustrated in the figure. Various types of joint pieces having open concave surfaces are included.

As described above, the present invention makes relay continuous casting by kundish exchange safe and easy, prevents accidents such as breakouts, and prevents mixing of components during relay continuous casting of different steel types, so that cut-off parts can be removed. The advantages of continuous casting are further enhanced, with excellent effects such as improved yield with reduced casting.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory views of the present invention, and FIG. 1 is a plan view showing a state in which a half-pipe piece of steel is placed on the molten metal surface of the previous charge in the mold. Fig. 2 is a vertical cross-sectional view schematically showing a joint where hot water from a later charge is poured onto the hot water from a previous charge in the mold, and the solidified shell of the previous charge shrinks on cooling to form a pipe. It is in a state where a half-shaped piece of steel is held. 1: Mold wall, 2: Molten steel from the previous charge, 2-size solidified shell, 3: Pipe half-shaped slab, 4: Molten steel from the next charge,
5: Side plate, 6: Notch.

Claims (1)

[Claims] 1. When performing continuous casting of multiple charges, a halved pipe-shaped piece of steel is placed with the concave side facing up on top of the molten steel of the previous charge in the mold, and the piece of steel is held in a solidified shell. A continuous casting method characterized by adding and casting a later charge of molten steel on top of the molten steel.